Growth and structural, optical and electrical properties study of bulk GaN

High-quality GaN substrates with a thickness of 0.5 to 1.2 mm were prepared by halide vapor-phase epitaxy (HVPE) on c-plane sapphire and by means of a post-growth laser-induced lift-off or natural stress-induced (self-) separation process. Structural, optical and electrical properties of the grown material were studied in detail. Resistivity and doping concentrations dependence on temperature were investigated and the results revealed a low donor concentration (2x10(15) cm(-3) at 273 K) and a moderate resistivity (10-48 Omega cm) of the samples. Several deep levels observed in the DLTS spectra were identified. The study shows that the GaN material is self-compensated and a strong influence of point defects related to dislocations on electronic transport is observed. The HVPE growth on InGaN/GaN multi-quantum wells buffer layers and subsequent self-separation method was seen as advantageous, in comparison to the laser-induced lift-off one, in respect to a lower cost and better crystalline quality of the GaN material obtained. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim